Transfer bridge for coarse bulk materials

ABSTRACT

A material handling apparatus may be employed to transfer discrete loads of excavated waste from an excavator or other excavation equipment to a dumping location beyond the reach of the excavator. The material handling apparatus may include a mobile bridge supported by two or more crawlers that enable movement of the mobile bridge. The material handling apparatus may further include a conveyance mechanism that transfers material between first and second ends of the mobile bridge. The conveyance mechanism may transfer material to haul trucks at the second end of the mobile bridge, which may be disposed above the first end of the mobile bridge. The conveyance mechanism may receive material from an intermediate transfer mechanism at the first end of the mobile bridge.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.15/912,122, entitled “Transfer Bridge for Course Bulk Materials” andfiled on Mar. 5, 2018, which is a continuation of U.S. patentapplication Ser. No. 13/882,148, now U.S. Pat. No. 9,908,716, entitled“Excavator Dump Range Extender” and filed on Apr. 26, 2013, which is aU.S. national stage application of International Application No.PCT/US2011/058180 filed on Oct. 27, 2011 and entitled “Excavator DumpRange Extender,” which claims the benefit under 35 U.S.C. § 119(e) ofU.S. Provisional Application No. 61/451,465, entitled “Excavator DumpRange Extender” and filed on Mar. 10, 2011 and of U.S. ProvisionalApplication No. 61/407,383, entitled “Excavator Dump Range Extender” andfiled on Oct. 27, 2010, all of which are hereby incorporated byreference in their entireties.

FIELD

The present disclosure generally relates to material handling devicesfor transferring discrete loads of excavated, uncrushed waste from anexcavator to a dumping location beyond the reach of the excavator.

BACKGROUND

In many surface mining and earthmoving operations, an excavating shovelor front-end loader is used to excavate waste material. These machinesprovide a discontinuous flow of excavated material by means of thediscrete loads discharged from their bucket or dipper at the end ofevery cycle. The waste material must then often be dumped at a locationthat is further from the excavated face than the dumping reach of theexcavator. Methods currently used to achieve this remote dumping includeuse of haul trucks, employing the excavator itself to re-handle thewaste, or loading the waste onto a conveyor system. However, when theexcavated waste contains rocks that are too large for safe and reliabletransport on a conveyor, a conveyor may only be used if the oversizedrocks are first screened out of the stream, or else crushed to aconveyable size. In other cases, the waste may be too wet, sticky orabrasive to be successfully carried by a conveyor.

When the distance to the dump location is of the order of two or threehundred feet, the methods described above may be expensive, or may haveother negative impacts such as diverting the excavator from advancingthe excavation, or consuming fossil fuels in wheeled vehicles.

SUMMARY

One embodiment of a material handling apparatus may take the form of amobile bridge and a first skip. The mobile bridge may include a firstend and a second end distal the first end. The first skip may beoperatively joined to the mobile bridge and configured for selectivepositioning between the first end and the second end of the mobilebridge. In some embodiments, the material handling apparatus may furtherinclude a second skip operatively joined to the mobile bridge andconfigured for selective positioning between the first end and thesecond end of the mobile bridge.

In some embodiments with first and second skips, the first skip may bemovably joined to a first track supported by the mobile bridge andextending between the first and second ends of the mobile bridge, thesecond skip may be movably joined to a second track supported by themobile bridge and extending between the first and second ends of themobile bridge, and the second track may be located at lower elevation onthe mobile bridge than the first track along at least a portion of themobile bridge located between the first and second ends of the mobilebridge. For other embodiments with first and second skips, the firstskip may be movably joined to a first track supported by the mobilebridge and extending between the first and second ends of the mobilebridge, the second skip may be movably joined to a second tracksupported by the mobile bridge and extending between the first andsecond ends of the mobile bridge, and the first track and the secondtrack may be positioned side-by-side along at least a portion of themobile bridge located between the first and second ends of the mobilebridge.

One embodiment of a material handling system may include a materialhandling device and an excavator. The material handling device mayinclude a mobile bridge and a first skip. The mobile bridge may includea first end and a second end distal the first end. The first skip may beoperatively joined to the mobile bridge and configured for selectivepositioning between the first end and the second end of the mobilebridge. The excavator may be operatively associated with the materialhandling device. In some embodiments of the material handling system,the material handling device may further include a second skip that isoperatively joined to the mobile bridge and configured for selectivepositioning between the first end and the second end of the mobilebridge. In such embodiments, the excavator may load the second skip withmaterial at the first end of the mobile bridge, and the second skip maydeposit the material at the second end of the mobile bridge.

A method of operating equipment in an excavation may include excavatinguncrushed material from a site using excavation equipment. The methodmay further include transferring, at a first end of a mobile bridge, theuncrushed material from the excavation equipment to a conveyancemechanism supported on the mobile bridge. The method may further includemoving the conveyance mechanism loaded with the uncrushed material fromthe first end of the mobile bridge to a second end of the mobile bridgethat is distal the first end of the mobile bridge. The method may alsoinclude unloading the uncrushed material from the conveyance mechanismproximate the second end of the mobile bridge. In some embodiments, theconveyance mechanism may be one or more skips. In other embodiments, theconveyance mechanism may be a conveyor, such as an apron or armoredconveyor.

Another embodiment of a material handling apparatus may take the form ofa mobile bridge and a conveyor. The mobile bridge may include a firstend and a second end distal the first end. The conveyor may beoperatively joined to the mobile bridge and configured to move materialsbetween the first end and the second end of the mobile bridge. In someembodiments, the conveyor may be an apron or an armored conveyor. Insome embodiments, the material handling apparatus may further include atransfer chute positioned proximate the first end of the mobile bridgeand configured to transfer a load to the conveyor at a controlled rate.In such embodiments, the transfer chute may include a latching door witha curved back.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows an elevation of a material handling or transfer device,viewed perpendicular to the long axis of the apparatus.

FIG. 2 shows a plan view of the device of FIG. 1, with the loading endshown on the left and the discharge end positioned to the right of thefigure.

FIG. 3 shows an isometric view towards the loading end of the device ofFIG. 1, with the device equipped with an intermediate load transfermechanism, such as a transfer bucket.

FIG. 4 shows an isometric view towards the discharge end the device ofFIG. 1, with the device equipped with a first skip and a second skip andthe second skip is in the dumping location.

FIG. 5 shows an isometric view of an intermediate load transfermechanism arrangement at the loading end of the device of FIG. 1.

FIG. 6 shows another view in elevation of the intermediate load transfermechanism arrangement.

FIG. 7 shows a schematic of an arrangement of the winding equipment todraw one of the skips back and forth along the device of FIG. 1.

FIG. 8 shows a schematic plan view of a working plan for the device ofFIG. 1.

FIG. 9 shows a schematic elevation view of a second embodiment of amaterial handling or transfer device.

FIG. 9a shows a schematic elevation of the second embodiment of thematerial handling or transfer device, showing the device loading a trucklocated on a bench that is lower than the bench where the excavationequipment is excavating material.

FIG. 9b shows a schematic elevation of the second embodiment of thematerial handling or transfer device, showing the device loading a trucklocated on a bench that is higher than the bench where the excavationequipment is excavating material.

FIG. 10a shows a schematic elevation view of a third embodiment of amaterial handling or transfer device.

FIG. 10b shows a schematic top plan view of the material handling ortransfer device shown in FIG. 10 a.

FIG. 11a shows a partial side elevation view of a fourth embodiment of amaterial handling device.

FIG. 11b shows an end elevation view of the material handling device ofFIG. 11 a.

FIG. 12a shows a partial top plan view of a fifth embodiment of amaterial handling device.

FIG. 12b shows a partial side elevation view of the fifth embodiment ofthe material handling device shown in FIG. 12 a.

FIG. 12c shows a partial top plan view of another embodiment of amaterial handling device that is similar to the material handling deviceshown in FIG. 12 a.

FIG. 12d shows a partial side elevation view of the embodiment of thematerial handling device shown in FIG. 12c , with the mobile bridgeomitted for clarity.

FIG. 12e shows a side elevation of another embodiment of a materialhandling device that is similar to the material handling device shown inFIG. 12a , with the mobile bridge omitted for clarity.

FIG. 13a shows a side elevation view of a material handling device in amining pit.

FIG. 13b shows a top plan view of the material handling device shown inFIG. 13 a.

FIG. 14a is a schematic plan view of another embodiment of a materialhandling device.

FIG. 14b is a partial schematic elevation view of the embodiment of thematerial handling device of FIG. 14 a.

DETAILED DESCRIPTION

Described herein are material handling devices for transferring discreteloads of excavated, uncrushed waste from an excavator to a dumping ordischarging location that may be up to a few hundred feet beyond thereach of the excavator. Also described herein are methods for operatingsuch a material handling device in cooperation with a discrete-loadexcavator such as a shovel or a front-end-loader.

In some embodiments, the material handling devices may take the form ofa mobile bridge supporting one or more skips that move between a loadingend and a dumping or discharging end of the bridge. Each skip may carrymaterial from a loading end of the bridge to a dumping or dischargingend of the bridge. After discharging its load, the empty skip may returnto the loading end to receive a new load of material. Whether or notmore than one skip is required may depend upon the cycle time of theexcavator. If the cycle time of the excavator is such that it would bedifficult to return a single skip back to the loading end in time forthe next load of material from the excavator, the material handlingdevice may be equipped with at least two skips. When so equipped, thecycles of the individual skips may be arranged so that one skip isloaded at more or less the same time that the other skip discharges itsload.

Each skip may be arranged to travel back and forth on a track and may bedrawn along the tracks by a winder or winch system, or otherarrangements such as cog wheels, friction-wheel drives, and linearmotors may be used. When two or more skips are used, one track may bepositioned over the other track, or the tracks may be positionedside-by-side. Further, the skip route may either be reciprocating on adedicated track for each skip, or the skips may be arranged to circulatefrom a track carrying only loaded skips to a return track carrying onlyempty skips. At the dumping end, the skips may be arranged to dump atdifferent locations, thereby providing for a more even distribution ofthe discharged material, or for discharging material into trucks thatdrive under the bridge abreast of each other.

The skips may either be filled directly from the excavator, or they maybe filled using an intermediate transfer mechanism, such as a transferbucket or chute that accepts the load from the excavator and then passesit to a skip. There may be one or more mechanisms or devicesincorporated into the support for the intermediate transfer mechanism tomitigate the impact and momentum transfer effects due to a load beingdropped from the excavator bucket into the intermediate transfermechanism. The intermediate transfer mechanism may be joined to themobile bridge.

An automated system may be implemented that co-ordinates the movementsof the intermediate transfer mechanism and the skips. To synchronize theexcavator, the intermediate transfer mechanism and the skips, thetransfer bucket may have a cycle time for each skip that is not longerthan the shortest average cycle time of the shovel. In this way, theintermediate transfer mechanism will be empty and in position to receivea load from the excavator when the excavator completes an excavationcycle.

FIG. 1 shows an elevation view of the material handling device. Thematerial handling device may include a mobile bridge 1. The mobilebridge 1, may include a support structure supported by at least twotravel crawlers. A first crawler 2 may be positioned near the loadingend of the mobile bridge 1, and a second crawler 3 may be positionednear the discharge end of the mobile bridge 1. Although tracked crawlersare shown in the figures, for smaller bridges, in some situations, thetravel drives may use multiple rubber-tired wheels instead of trackedcrawlers.

At a first end 4 of the mobile bridge is a loading area, and at thesecond end 5 distal from the first end is a discharge area. At leastsome of the machinery and controls for the mobile bridge 1 may be housedin a machine house 6. The bridge support structure may be formed using atruss. To allow for a lighter truss structure, a mast and suspensionrope arrangement 7 may be joined to the truss to help to support theloads that travel on the truss. The bridge support structure may bedesigned to support itself and one or more loaded skips 12, 13. In someembodiments, the bridge support structure may be designed to support askip 12, 13 containing a load of up to approximately 100 tons.

The truss may include a first rail track 8 for a first skip 12, and asecond rail track 9 for a second skip 13. The first and second skips 12,13 may each include flanged wheels that run on rails, as is common forore carts and the like. The first rail track 8 may be located above thesecond rail track 9. In the loading zone 4, the first and second railtracks 8, 9 may converge in a loading zone 10 of the mobile bridge 1.This convergence allows the first and second skips 12, 13 to be loadedat a similar height. To allow the convergence of the first and secondskips 12, 13 at this location, the structural cross-members that wouldotherwise run between the rail tracks may be omitted in the area ofconvergence, and the beams supporting the rail tracks may be madecommensurately deeper. In other embodiments, the maximum loading heightof an excavator, such as a shovel, together with the height of the firstand second skips 12, 13 and the spacing between first and second railtracks 8, 9 may be such that no convergence in the rail tracks 8, 9 isrequired for easy skip 12, 13 loading, allowing the first and secondrail tracks 8, 9 to remain parallel to each other (in elevation view)throughout the loading zone 10.

An intermediate transfer mechanism 11, such as a transfer bucket ortransfer chute, may be positioned proximate the loading zone 10. Theintermediate transfer mechanism 11 may receive the material from thebucket of the excavator or other excavation equipment, and then maytransfer the material to a first skip 12 positioned with the loadingarea 10. While the first skip 12 is loaded, the second skip 13 may bepositioned in the discharge area to discharge its load. In someembodiments, the intermediate transfer mechanism 11 may receive a loadfrom the excavation equipment before one of the first or second skips12, 13 arrives within the loading area 10. In these embodiments, theintermediate transfer mechanism 11 may be set up hold the load until oneof the first or second skips 12, 13 arrives in the loading area 10. Onceone of the first or second skips 12, 13 arrives in the loading area 10,the intermediate transfer mechanism 11 may transfer the load to the skip12, 13.

The mobile bridge 1 and the first and second skips 12, 13 may bedesigned so that the cycle times for each skip 12, 13 to travel from theloading end 4 to the discharge end 5 and back to the loading end 4 ofthe mobile bridge 1 may be less than twice the cycle time of theexcavator. Further, the first and second skips 12, 13 and the mobilebridge 1 may be configured so that no excessive accelerations or speedsare required for each skip 12, 13 to cycle between the loading anddischarging ends of the mobile bridge 1 within two cycles of theexcavator. One potential benefit of cycling the first and second skips12, 13 from the loading end 4 to the discharge end 5 and back to theloading end 4 of the mobile bridge 1 within two cycles of the excavatoris that a skip 12, 13 will always be available for the excavator todischarge its load, thus improving the efficiency of the excavatingoperation. For example, if the typical cycle for the excavator is thirtyseconds, then the first and second skips 12, 13 would each move from thefirst or loading end 4 to the second or discharge end 5 of the mobilebridge 1, deposit the load at the second or discharge end 5 of themobile bridge 1, and return to the first or loading end 4 of the mobilebridge 1 to receive another load within sixty seconds.

In other embodiments of the material handling device, when more than onerail track is required, the tracks may be arranged side-by-side on thebridge truss instead of the over-under arrangement described above. Insuch an embodiment, the motion of the intermediate transfer mechanism 11in moving from one skip loading position to another may be primarilyhorizontal (or in directions substantially transverse to thelongitudinal axis of the mobile bridge 1) rather than vertical.

In some embodiments, the mobile bridge 1 may utilize a single skip. Insuch embodiments, the skip may be configured to cycle between the firstend 4 and the second end 5 of the mobile bridge 1 in less than oneexcavation cycle. For example, if the typical excavation cycle is thirtyseconds, then the skip may move from the first end 4 to the second end 5of the mobile bridge 1, deposit its load at the second end 5 of themobile bridge 1, and return to the first end 4 of the mobile bridge 1 toreceive another load within thirty seconds.

FIG. 2 shows a plan view of the material transferring device, with theloading or first end 4 shown on the left-hand side of the page and thedischarge or second end 5 positioned on the right-hand side. Theintermediate transfer mechanism 11 may be sized to provide asufficiently expansive target for receiving a load from the excavationequipment, such as a shovel or the like. The skips 12, 13 may be sizedso that any rock or other material that passes through the excavator'sbucket does not get stuck in a skip. In this embodiment, the skips 12,13 may be equipped with bottom-dump doors for discharging their load ofrock and other material in the discharge zone. In other embodiments, theskips 12, 13 may be arranged for other dumping methods, includingside-dump or forward dump. However, these other dumping methods tend torequire more time, and thus may reduce the overall productivity of themachine.

In the embodiment shown in FIG. 2, the structural cross-members betweenthe truss chords are omitted in the loading zone at the location 15where the first and second skips 12, 13 converge. Omitting thesecross-members allows for the convergence of these skips 12, 13. Theskips 12, 13 may converge at the first end 4 at approximately a commonelevation. In some embodiments, the common elevation may beapproximately halfway between the elevations of the first rail track 8and the second rail track 9 when the first rail track 8 is located abovethe second rail track 9. The system that draws the skips 12, 13 back andforth along the mobile bridge 1 may be synchronized so that the firstand second skips 12, 13 do not interfere with each other in the area ofthe converging rail tracks 8, 9. In particular, the system may be set upto position only one of the first and second skips 12, 13 within theloading area at a given time.

In the dumping area, the structural cross-members between the trusschords may also be omitted at the second end portion of the bridge wherethe first skip 12 dumps its load. Similarly, the area below where thesecond skip 13 dumps its load may also be free of horizontalcross-members to allow material to fall without impacting any structure.The dumping zone for the first skip 12 may be located closer to thedischarge end 5 of the mobile bridge 1 than the dumping zone for thesecond skip 13.

FIG. 3 shows an isometric view towards the loading end 4 of the device.A slew bearing (not visible in this view) may be mounted between thebridge structure and the crawler 2. A deflection sheave may incorporatea tensioning arm 34. The deflection sheave may be positioned proximatethe machine house 6. The deflection sheave may redirect a flexiblemember, such as a winding rope or wire, that passes to a winding drum inthe machine house 6.

FIG. 4 shows an isometric view towards the discharge end 5 of the devicewhen the device includes the first and second skips 12, 13. The crawler3 may support the bridge truss via an axial adjustment mechanism 16 thatallows the crawler 3 some axial movement relative to the bridge truss,so that the two crawlers 2 and 3 supporting the bridge have a degree oftranslational freedom relative to each other.

FIG. 5 shows an isometric view of an intermediate transfer mechanism 11(e.g., a transfer bucket) positioned at the loading end of the device.The intermediate transfer mechanism 11 may incorporate a sloped oroblique receiving face 17 onto which the excavation equipment drops itsload. The receiving face 17 may reduce the impact sustained by theintermediate transfer mechanism 11. The receiving face 17 of theintermediate transfer mechanism 11 may have a predetermined width thatis greater than the width of the excavator bucket to help minimize theamount of material that is dumped outside the intermediate transfermechanism 11. The intermediate transfer mechanism 11 may include adischarge end 25. The discharge end 25 may be tapered to guide materialinto a skip 12, 13 that may be narrower than the receiving face 17 ofthe intermediate transfer mechanism 11. It may be desirable to haveskips 12, 13 that are wide enough to allow the largest rocks deliveredby the excavator to pass through, but not so wide as to require a bridgetruss with a disproportionate width.

With continued reference to FIG. 5, the intermediate transfer mechanism11 may be supported by at least a pair of shock-absorbing mechanisms 18to reduce the rate of impact and fatigue damage to the intermediatetransfer mechanism 11 and its support structures. Shock-absorbingmechanisms may alternatively, or additionally, be incorporated into theshock frames 19 or the pair of hydraulic cylinders 20 (note only onecylinder 20 is fully visible in this view.) The shock-absorbingmechanisms 18 may be similar to the shock-absorbers used on heavytrucks, such as oil and nitrogen shocks or rubber or other polymerspring shocks.

The hydraulic cylinder 20 may serve to tip the intermediate transfermechanism 11 so that its contents slide into the waiting skip 12, 13.The receiving face of each skip 12, 13 may be slanted. The relativepositions of the tipping intermediate transfer mechanism 11 and eachskip 12, 13 may be configured so that the rock slides rather than fallsfrom the intermediate transfer mechanism 11 into the skip 12, 13.

Even with the use of converging rails, the receiving face of the firstskip 12 when positioned to receive a load may be at a different heightabove some datum compared to the receiving face of the second skip 13when similarly staged. Therefore the intermediate transfer mechanism 11may be supported by pair of hydraulic cylinders 22 that raise and lowera lift frame 21 as needed for loading either the first skip 12 or thesecond skip 13. The lift frame 21 may pivot at a pin 23 positioned at apredetermined point so as to provide for the desired movement of theintermediate transfer mechanism between its different heights.

The movement of the intermediate transfer mechanism 11 may be selectedto best suit the relative heights of the excavator bucket at dumping andthe skips 12, 13 when receiving load. For example, the intermediatetransfer mechanism 11 may always receive load from the excavator at thesame height that is necessary for loading the first or top skip 12, andthen it may be lowered to transfer its load into the second or bottomskip 13. The incorporation of the intermediate transfer mechanism 11into the mobile bridge 1 may help to reduce the potential for therequired discharge height of the shovel bucket to be out of reach, evenwhen the configuration of the first skip 12 positioned above the secondskip 13 is used. It also serves to keep the dump point for the shoveldipper at approximately the same height for every cycle, regardless ofwhich skip 12, 13 is loaded. Since the intermediate transfer mechanism11 may be returned to the “ready to receive” position as soon as it hasdischarged its load into a skip 12, 13, the use of the intermediatetransfer mechanism 11 also provides a structure for the excavationequipment to dump its load even if the excavation equipment's cycle iscompleted before an empty skip 12, 13 arrives back at the loading area.

FIG. 6 shows a more direct view in elevation of the intermediatetransfer mechanism 11. In this view, the sheaves 26 deflecting theflexible members 33 for the first skip 12 are shown, and one of the pairof sheaves 27 for the second skip 13 is visible. The flexible members 33may take the form of ropes, wires, or the like.

FIG. 7 shows a schematic of an arrangement of the winding or tractionequipment to draw the skips 12, 13 back and forth along the mobilebridge structure 1. This arrangement advantageously keeps the flexiblemembers 33 clear of the paths of material both entering and exiting theskips 12, 13. Further, such an arrangement keeps the flexible members 33outside of paths traversed by the first and second skips 12, 13 as thefirst and second skips 12, 13 move between the first and second ends 4,5 of the mobile bridge 1. In particular, a square outlined by brokenlines represents the first skip 12. The first skip 12 may be attached toa pair of flexible members 33 via an articulating drawbar 32. Thedrawbar 32 may be provided to compensate for the change in height of thefirst skip 12 relative to the ropes as it travels on the convergingportion of the rail tracks 8. Each flexible member 33 may run on oneside of the first skip 12, within the vertical braces of the bridgetruss. Deflection sheaves 26, if oriented in a horizontal plane asshown, may take the flexible members 33 to the outside of the trussstructure. A further two pairs of deflection sheaves 28 may be mountedon articulated tensioning arms 34 to redirect the flexible members 33upwards towards a pair of double winding drums 29.

Each half of each winding drum 29 has one end of a flexible member 33joined to it in such a manner so that it is wound in a differentdirection from the other end of the flexible member 33 joined to thewinding drum 29. Accordingly, as one end of the flexible member 33 iswound onto the winding drum 29, the other end of the flexible member 33is unwound. The winding drums 29 may be on a common shaft and driven ina conventional manner by a gear reducer 30 and a motor 31. The speed ofthe motor 31 may be controlled by a variable frequency drive or othersuitable means. While the winding arrangement is described in connectionwith the first skip 12, a similar arrangement may be used for the secondskip 13.

FIG. 8 shows a working plan of the device of FIG. 1 for a situationwhere the excavation equipment is advancing in a direction parallel tothe long axis of a strip mine or similar excavation site, such as acanal. This direction is shown by the arrow in FIG. 8. The face about tobe excavated in the next traverse of the excavation equipment 35 haspreviously been formed at area 36. The face may be at an obtuse anglerelative to a high wall 100 of the excavation site. The trough fordumping the waste is at dumping area 37, and the part of the trough thathas been backfilled during previous passes is located at backfill area38, which is behind the edge of the bench 39 formed during previouspasses.

As the excavation equipment 35 starts to advance down the face from thehigh wall 100, the mobile bridge 1 may be positioned so that alongitudinal axis of the mobile bridge 1 is approximately parallel tothe face. As the excavation equipment 35 advances down the face, thedischarge end 5 of the mobile bridge 1 may swing away from the face. Thelocations of the crawlers 3 near the discharge end 5 of the mobilebridge 1 are indicated by a succession of squares, shown as thereceiving end 4 of the mobile bridge 1 moves down the face incoordination with the excavation equipment 35. As the receiving end 4 ofthe mobile bridge 1 moves down the face, the discharge end 5 may swingoutwards and rearwards in an arc. The succession of chords 40 shows theangle of the longitudinal axis of the mobile bridge 1 in successivepositions. The succession of circles 41 shows the dumping positions forthe first and second skips 12, 13 as the mobile bridge 1 moves tosuccessive positions. These successive positions may result in theuncrushed material being deposited from the mobile bridge 1 in an arcshaped path in the backfill area 38. When the excavation equipment 35has completed its traverse down the face, it and the mobile bridge 1both return to the starting position for a new cut.

FIG. 9 shows another embodiment of the material transfer device. Thesecond material transfer device may be used to load haul trucks 105.This embodiment may be useful when the excavation equipment 35 (e.g., ashovel) is working in crowded conditions or the footing may be difficultfor trucks 105. It also eliminates the significant risk of impactsbetween the shovel's dipper and the haul trucks 105 and may improve theloading speed for the trucks 105. In this embodiment, the skip rails forthe skips 42, 43 may be arranged to minimize the dump height of materialfalling into the truck bodies. The discharge end 5 of the mobile bridge1 may also be equipped with one or more transfer buckets or chutes tofacilitate gentler loading of the trucks 105. As shown in the figures,the bridge structure for the mobile bridge 1 may be arched. Further, theloading end 4 of the mobile bridge 1 may be positioned at a lowerelevation than the discharge end 5 of the mobile bridge 1. Such aconfiguration may allow for the skips 42, 43 to be loaded at a lowerelevation and discharged at a higher elevation. In some embodiments,such as shown in FIG. 9a , the trucks 105 may be positioned on a lowerbench than the excavation equipment. In other embodiments, such as shownin FIG. 9b , the trucks may be positioned on a higher bench than theexcavation equipment.

FIG. 10(a) shows yet another embodiment of a material transfer device,where the material is being moved along a slope. In this case the upperportion of a sloping bank of material 44 is excavated, shown in FIG.10(a) in a sectional elevation. The dashed lines show the originalsurface 45 or contour of the bank prior to excavation. The solid lineshows the profile of the bank during excavation. At excavation area 47is a bench that has been created by the progress of the excavationequipment 35, and at discharge area 48 there is a bench prepared bybulldozing or other means. The crawlers of the mobile bridge 1 rest onthese two benches. The carried material may be discharged into amined-out area 46 at the second end 5 of the mobile bridge 1. For thisembodiment the rail tracks 8, 9 of the skips 12, 13 may follow a curvein the vertical plane, and a guidance mechanism or system may beprovided for the flexible members 33 to have them follow the curve. FIG.10(b) shows a plan view of FIG. 10(a), now also showing the position ofthe excavation equipment 35 that is excavating a face 49. The arrowshows the direction of excavation.

FIG. 11a shows a side elevation of the loading end 4 of anotherembodiment of a material handling device, and FIG. 11b shows an end viewof the material handling device. FIG. 11b is symmetrical about thecenterline. However, in order to show certain details, not all elementsare shown on both sides of the centerline. The material handling devicemay be similar to the device shown in FIG. 1, and operate in a similarmanner, except as noted in the following paragraphs.

For this embodiment of the material handling device, the loadingposition for both the first skip 12, which may also be referred to asthe top or upper skip, and the second skip 13, which may also bereferred to as the bottom or lower skip, is at a decreased elevationcompared to the version shown in FIG. 1. This may be achieved byarranging for the first rail track 8, which may also be referred to asthe top or upper rail track, to converge to the level of the second railtrack 9, which may also be referred to as the bottom or lower railtrack. Further, the lower rail track 9 does not rise toward the loadingpoint. In sum, the upper rail track 8 and the lower rail track 9 mayconverge towards the elevation of the lower rail track 9. In FIG. 11a ,the position that the top skip 12 occupies when positioned within theloading area is shown by a dashed outline.

This arrangement allows the intermediate transfer mechanism 50, whichmay take the form of a transfer chute, to discharge the load of materialinto either of the first or second skips 12, 13 without the need for aseparate tipping action by the intermediate transfer mechanism 50.Because both skips 12, 13 may be at a relatively low level to the groundwhen loaded, the intermediate transfer mechanism 50 may receive the loadfrom the shovel, loader, or other excavation or loading equipment andtransfer the load to the skips 12, 13 by means of a simple chute action,rather than a tipping action. The decreased elevation of the skips'loading position facilitates using an intermediate transfer mechanism 50that receives load from the shovel and transfers the load to the skips12, 13 via a chute action while not having its top edge beyond the upperreach of the shovel, loader or other excavation or loading equipment.Once the shovel or loader dumps the material into the intermediatetransfer mechanism 50, the material simply slides down the angled bottomof the chute into a waiting skip 12, 13.

To achieve this type of skip convergence, the gauge of the lower railtracks 9 may be narrower than that of the upper rail tracks 8. Since thespan of the skip wheels may correspond to their respective rail gauges,the span between the top skip's wheels may be wider than that of thelower skip's wheels. In the area where the upper rail track 8 is slopingdown towards the loading position, it may be supported on a beam 57 orthe like that slopes accordingly.

The intermediate transfer mechanism 50 may be supported on the bridgesupport structure at a pair of pinned connections at points 51, and alsoby a pair of supports at pinned connections 52. These latter supportsmay include shock absorbing mechanisms 53 that transfer the dumpingimpact loads directly into a foot element 54 that rests on the ground.The shock absorbing mechanisms 53 may be similar to the shock absorbersused on heavy trucks, such as oil and nitrogen shocks or rubber or otherpolymer spring shocks. The foot element 54 may be articulated to betteradapt to uneven ground.

The loading end 4 of the bridge support structure may also rest on thefoot element 54 to better absorb the impact and dead loads of thematerial dumped by the excavator or other excavation equipment. The loadpath between the bridge support structure and the foot element 54 may bevia a support link 55 so that when the support link 55 is tilted by ahydraulic cylinder 56 or the like, the foot element 54 may be liftedclear of the ground to allow relocation of the mobile bridge 1. Thepoints where the support link 55 is joined to the bridge supportstructure, the hydraulic cylinder 56, and the foot member 54 may beselected so that when the foot element 54 is raised from a loweredposition on the ground to a raised position, the foot element 54 isinitially moved from the lowered position to the raised position by ashearing or sliding movement. Such a shearing or sliding movement mayhelp to minimize the suction effect that may occur when trying to raisethe foot element 54 directly up out of wet or sticky ground.

The link arrangement that involves joining the intermediate transfermechanism 50 to bridge structure via the pins 51 and to the foot member54 via the supports and the shock absorbing mechanisms 53 and furtherinvolves joining the hydraulic cylinder 56 to the foot element 54 andthe bridge structure via the support link 55 also helps to protect thehydraulic cylinder 56 from carrying large impact dumping loads. Inparticular, since the hydraulic cylinder 56 is joined to the supportlink 55 while the dumping energy from the loads deposited by theexcavator onto the intermediate transfer mechanism 50 are primarilydirectly transferred into the ground via the foot element 54 through thesupports and shock absorbing mechanisms 53 that are joined to the footelement 54 and that at least partially support the intermediate transfermechanism 50, the hydraulic cylinder 56 will generally have little to nodumping energy transferred to it.

FIG. 12a is a partial top plan view of a fifth embodiment of thematerial transfer device, and FIG. 12b is a partial side elevation viewof the material transfer device shown in FIG. 12a . This embodiment issimilar to the fourth embodiment of the material transfer mechanism withone difference between the embodiments occurring with respect to amodification of the intermediate transfer mechanism.

In this fifth embodiment, the intermediate transfer mechanism 50 maytake the form of a transfer chute with a discharge door 58. Thedischarge door 58 controls when material placed in the transfer chutedischarges into a waiting skip 12, 13 or other conveyance mechanism.This allows the excavator or other excavation or loading equipment todump its load into the transfer chute at any time, even when a skip 12,13 is not positioned at the discharge end of the transfer chute. Anotheradvantage of the discharge door 58 is that it stills the kinetic energyof dumped material, helping to bring it to rest before being discharged,now with less energy, into a waiting skip 12, 13. This function allowsthe skips 12, 13 to be lighter and less robust than otherwise necessaryin the absence of this reduction of energy. To assist in this stillingfunction, the back 63 of the discharge door 58 may be curved so as topresent its surface tangentially to large rocks that have rolled down tothe bottom of the transfer chute. Also, the back 63 of the dischargedoor 58 may incorporate a suspended bed of resilient material to furtherreduce shock loading on the discharge door 58.

Another function of the discharge door 58 is to discharge material intoa skip 12, 13 in a controlled manner, so that a partially-openeddischarge door 58 will at first allow only finer material to flowthrough the opening and into the skip 12, 13, thus providing a bed ofmaterial that may help to protect the skip 12, 13 from large rocksfalling from the transfer chute. Only when a large enough openingbetween the door 58 and the transfer chute is formed will large rocks beable to pass through and fall onto the bed of material already collectedin the skip 12, 13 below.

Any number of particular arrangements of the discharge door 58 arepossible, but one arrangement incorporates a horizontal hinge 64positioned on an upper surface of the intermediate transfer mechanism50. In this configuration, a pair of latches 60 holds the door 58closed, and hydraulic cylinders 59 or equivalent control the opening andclosing of the door 58. The hydraulic cylinders 59 may be supported by aframe 62 that carries impact forces back into the end of the transferchute. This helps to ensure that when the transfer chute assembly pivotsabout pins 51 under shock loads, all the connected elements of the doormechanism move in concert. In some embodiments, instead of employinglatches 60 to hold the discharge door 58 in the closed position, toggleor over-center linkages may be used.

A discharge lip of the transfer chute may be equipped with a rock shelf61 configured to impede acceleration of large rocks as they slidetowards a waiting skip 12, 13. To minimize the potential for the rockshelf 61 to interfere with tall rocks projecting upwards from the rearof the skip 12, 13, the rock shelf 61 may be attached by a horizontalhinge 65 that allows the shelf to swing upward if pushed by a rock fromthe rear.

With reference to FIGS. 12c and 12d , the transfer chute may beconfigured to regulate the rate of transfer from an excavator to anendless conveying device, such as a belt conveyor, armored conveyor orapron conveyor, in such a way that the large discrete loads from theexcavator are gradually discharged onto the endless conveyor 200 so asnot to exceed the containment capacity of the conveyor. The endlessconveyor 200 may move the transferred material from the first end to thesecond end of the mobile bridge. For clarity, the mobile bridge is notshown in FIGS. 12c and 12d . However, the mobile bridge may be similarto the mobile bridges shown in other embodiments of the materialtransfer device. At the second end of the mobile bridge (not shown), theconveying device or other conveyance mechanism may deposit the materialonto the ground or into a haul truck 105 or the like.

The transfer chute may be configured to regulate the flow of materialonto a conveyor by a gradual and controlled opening of the dischargedoor 58, allowing the material to slide under the influence of gravityonto the conveyor 200. Discharging the load in this manner helps toavoid the high shearing loads that the conveyor 200 would otherwise haveto exert to draw the material out of a deep pile. This method may beparticularly attractive where only enough loading regulation is requiredso as not to overflow the conveyor 200, rather than where very evenregulation is desired as in the case of feed to a crusher. Because ofthe lower conveyor tensions that arise, this method allows for longerand steeper apron and armored conveyors than might otherwise be thecase.

FIG. 12c shows a schematic of an embodiment of the material handlingdevice where a transfer chute 210 with a discharge-regulating door 58feeds onto an apron conveyor. The apron conveyors may include partiallyoverlapping armored plates 101 that are carried by crawler-tractor chainthat rides on rollers supported by a bridge structure, which is notshown for clarity purposes. The armored plates or aprons may havevertical overlapping wings 95 to contain a pile of material on theplates with limited spillage. The endless conveyor 200 may be drawn by ahead sprocket 93 and return via carry rollers 98 to a tail sprocket 92.The endless conveyor 200 may be oriented at a range of angles to thehorizontal. Where a convex curve is required for the endless conveyor200, restraining rollers 96 outboard of the overlapping wings 95 mayserve to prevent uplift of the tensioned chains. The material dischargedby the transfer chute 210 and door 58 may at first be formed andcontained by skirtboards 99 until suitably-contained piles of material205 have formed on the plates 101. An advantage of using overlappingwings 95 of substantial height is that friction between the materialpiles and a great length of static skirtboard is avoided, thus reducingthe tension and power demand on the chain and drives. Alternatively,static skirtboards may be used for part or all of the conveyor's length.

Although the schematic shows an apron conveyor where the support rollersare fixed to the support structure, other types of conveyors, such asthose where rollers are joined to some plates and the rollers in turntravel on rails supported by the bridge structure, may be preferred insome cases. Also, in cases where the uncrushed rock is not too large,the carrying element may be a heavy-duty conveyor belt that is supportedin the conventional way by fixed idlers. Another embodiment of thematerial handling device may transport the material on a conveyor beltcarried on wheel-supported frames, slings or carts that in turn travelon rails supported by the mobile bridge. In such embodiments, it may beconvenient to arrange for the belt itself to be the primary means thatdraws the wheeled frames or carts along with it. One advantage ofwheel-mounted frames to carry the conveyor belt is that large rocks donot impinge on static idlers as the conveyor progresses, so that thebelt may carry much larger rocks than could otherwise be carried on afixed-idler conveyor.

FIG. 12e shows a schematic elevation of an embodiment of the materialhandling device where a transfer chute 210 discharges in a controlledmanner, via a discharge door 58, material onto an endless belt conveyor200 that is carried by wheel-mounted frames 215. The transfer chute andconveyor combination may be carried on a mobile material transferdevice, or else on material transfer device that is not mobile. The beltconveyor 200 may have a drive pulley 220, a tail pulley 225, and bendpulleys 230. In an area where the belt 235 of the conveyor 200 is nolonger supported by wheel-mounted frames 215, the belt 235 may besupported by other means such as garland idlers 280. On the return run,the belt 235 may be supported by return idlers 240. The wheeled frames215 carrying the belt 235 may be spaced apart and travel on carry rails245 on the carry side and on return rails 250 on a return side. At apoint before the belt conveyor head pulley, the train of wheeled framesmay be guided around a head wheel 255 by a guide arrangement 260. At apoint before reaching the belt conveyor tail pulley, the train ofwheeled frames may be guided around a tail wheel 265 by a second guidearrangement 270. The plurality of wheeled frames may be connected toeach other by flexible connection members 275 in order to maintain therequired spacing between the wheeled frames. The wheeled frames mayincorporate a rigid bar formed into the shape of a trough that spansbetween a left-hand pair of carrying wheels and a right-hand pair ofcarrying wheels and supports the belt 235 directly, or else the belt 235may be carried on a flexible member that spans across the wheeled framefrom a left side to a right side of the wheeled frame.

FIGS. 13a and 13b show a strip mining pit with a material handlingdevice positioned within the strip mining pit to transfer materialacross the pit. The figures further show one potential way to lay outthe mining pit to be compatible with operation of any of the materialhandling devices described above.

Carrying overburden directly over the mined-out area of a stripmine—rather than around the end of the strip—is an efficient way ofdealing with overburden. However, in many cases, such “cross-pit”transfer first requires the overburden to be crushed before it can becarried on a belt conveyor across the pit. Also, the arrangement of thecross-pit equipment must be such that there is minimal interference withthe operations on the pit floor that are excavating and hauling themineral.

With reference to FIG. 13a , the material handling device may beconfigured to transfer excavated overburden from the lowest overburdenbench 70 of a strip mine, first over a mineral bench 68 and then over amined-out strip 73 to a spoils dumping location 69 to form a lowestwaste bench. The material handling device may be partially supported bya tower 67 whose crawlers rest on a portion of the mined-out area. Asecond set of crawlers resting on the mineral bench 68 may complete thesupport of the material handling device, with suitable provision madefor automatic accommodation of the tendency of the two sets of crawlersto move closer to or further from each other. To allow access formineral excavators and mineral haulage, the crawlers and the tower 67may be sized and the mine may be excavated in such a manner to allow fora corridor of at least fifty feet width between the crawlers and a benchof the mine. More particularly, the lowest bench and the lowest wastebench may be created to be sufficiently spaced apart to allow forsufficient space on the floor of the mine between the these two benchesso that mineral excavation operations may occur on the floor of the minewith the tower 67 of the mobile conveyor also supported on the floor.The ghost lines 71 show the position of the crawlers when the materialhandling device is advanced to keep pace with the overburden excavator,at a time before the mineral in bench 125 is excavated. In this lattercase the access corridor is now located on the spoil side of thecrawlers.

With reference to FIG. 13b , a potential position of the excavationequipment 72 or the like working in the lowest overburden bench 70 isshown relative to the material handling device.

The proportions shown in FIG. 13 are typical of the pit and equipmentarrangements that might apply to a strip coal mine in the Western U.S.,and are shown only because the feasibility of cross-pit transferarrangements may be highly dependent on the geometric arrangementadopted. For example, the height of the overburden bench may beapproximately 50 feet, the width of the mineral bench may beapproximately 115 feet, the depth of the mineral bench may beapproximately 70 feet, the width of the floor may be at leastapproximately 100 feet, and the lowest waste bench may have a sloperelative to the floor of approximately 38 degrees. Additionally, thedistance between the face of the lowest overburden bench (at its lowerend) at the point of excavation to the floor may be approximately 115feet or so, and the distance from the face to the first end of themobile bridge may be approximately may be approximately 15 feet or so.Further, the distance from the first end of the mobile bridge to thesecond end may be approximately 320 feet, and the distance between themain portion of the mobile bridge structure and the floor may be greaterthan 70 feet. Other geometries, proportions and dimensions may beequally applicable for other mines and/or material handling devices.

Note also that the method and arrangement shown in FIG. 13 is notrestricted to the type of material handling devices described here,where uncrushed overburden is carried in discrete loads by skips. Themethod and arrangement would apply equally to other methods of carryinguncrushed overburden, for example by substituting one or more apronfeeders for the skips that carry the uncrushed material across thebridge.

In another embodiment of the material handling device, when more thanone rail track is required, the tracks may be arranged side-by-side onthe bridge truss instead of the over-under arrangement describedearlier. A variation of this other embodiment of the material handlingdevice is shown in FIGS. 14a and 14 b.

FIG. 14a is a schematic plan view of this variation, where a mobilebridge 74 is configured to carry first and second skips 75, 76 travelingparallel to each other on horizontally adjacent tracks. An intermediatetransfer mechanism 11 may be positioned at a first end of the mobilebridge 74 to feed the first and second skips 75 and 76. The intermediatetransfer mechanism 11 may take the form of a first transfer chute 77 anda second transfer chute 78. The transfer chutes 77, 78 may or may not beequipped with a discharge door that functions similar to the dischargedoor 58 of FIGS. 12a and 12b . Each skip 75, 76 may be drawn to and froas needed by flexible members 81 that run within each skip's travel way.If necessary, the flexible members 81 may be supported against sag byplacing the fore and aft attachment points to the skips 75, 76 at a lowpoint on the skips 75, 76, and providing support rollers at the level ofthe skip tracks to prevent excessive sag between the terminal bendsheaves 80 and the attachment to the skips. The bend sheaves 80 at eachend of the mobile bridge 74 (not visible below the transfer chutes inFIG. 14a ) redirect the flexible members 81 to the outside of the mobilebridge 74 and towards locations 82 where winding drums provide thetraction, or alternatively where additional deflection sheaves redirectthe flexible members 81 to a machine house at a different level as insome of the embodiments previously described.

FIG. 14b is a schematic elevation view of the material handling deviceshown in FIG. 14a , where the mobile bridge 74 is shown partiallysectioned at the first or loading end to better illustrate thearrangement of the first skip 75 relative to the intermediate transfermechanism 11, such as a transfer chute. The intermediate transfermechanism 11 may be supported by at least a pair of dampened suspensionelements 90 that are pinned at a plate 84 to the main body of theintermediate transfer mechanism 11 and by the mobile bridge 74 via apinned connection 83 between the mobile bridge 74 and main body of theintermediate transfer mechanism 11, or the intermediate transfermechanism 11 may be supported by some other suitable arrangement. Thefirst and second skips 75, 76 may be configured to discharge their loadsat the second or discharge end of the mobile bridge 74. The dumping endof the mobile bridge 74 may be designed to omit structure elements belowthe dumping locations to provide a clear fall for material dischargedfrom the first and second skips 75, 76.

Each intermediate transfer mechanism 11 may be configured to extend outbeyond one side of the bridge structure so as to provide a sufficientlyexpansive target for the excavator or other excavation equipment totransfer loads from the excavation equipment to the intermediatetransfer mechanisms 11. The intermediate transfer mechanisms 11 mayeither be structurally separate from each other or they may bestructurally joined to each other. By positioning the bridge roughlysuch that its longitudinal axis intersects with the slewing axis of theexcavator, the excavator will be able to dump into either intermediatetransfer mechanism 11 without having to traverse.

The mobile bridge 74 may be supported at the loading end by a set ofcrawlers 85 connected to the underside of the bridge structure through aslew bearing 86. A second set of crawlers 85 located towards thedischarge end of the bridge may be connected to the underside of thebridge structure through a slew bearing 86 as well as a mechanism suchas the bogie and rails assembly 87 allowing that set of crawlers 85 someindependent longitudinal movement relative to the bridge structure.

In order to support the undesirable moments developed by theasymmetrical loading of the bridge structure due to only oneintermediate transfer mechanism 77, 78 or skip 75, 76 being loaded at atime, the slew bearings 86 may either be of the “closed” type that isdesigned to hold against an overturning load, or else they may be of the“open” type found on large mining shovels where the bearing's largediameter ensures that the center of load is always within the arc ofsupport provided by the bearing rollers.

An advantage of this side-by-side configuration is that it is easier toarrange for each skip 75, 76 to be able to dump its load over a longerdistance at the end of the bridge. Another advantage is that no specialstructural device is needed to have both skips 75, 76 capable ofdischarging their respective loads at a lower elevation of the mobilebridge 74, as is desirable when loading into haul trucks.

All directional references (e.g., upper, lower, upward, downward, left,right, leftward, rightward, top, bottom, above, below, vertical,horizontal, clockwise, and counterclockwise) are only used foridentification purposes to aid the reader's understanding of theembodiments of the present invention, and do not create limitations,particularly as to the position, orientation, or use of the inventionunless specifically set forth in the claims. Connection references(e.g., attached, coupled, connected, joined, and the like) are to beconstrued broadly and may include intermediate members between aconnection of elements and relative movement between elements. As such,connection references do not necessarily infer that two elements aredirectly connected and in fixed relation to each other.

In some instances, components are described with reference to “ends”having a particular characteristic and/or being connected with anotherpart. However, those skilled in the art will recognize that the presentinvention is not limited to components which terminate immediatelybeyond their points of connection with other parts. Thus, the term “end”should be interpreted broadly, in a manner that includes areas adjacent,rearward, forward of, or otherwise near the terminus of a particularelement, link, component, part, member or the like. In methodologiesdirectly or indirectly set forth herein, various steps and operationsare described in one possible order of operation, but those skilled inthe art will recognize that steps and operations may be rearranged,replaced, or eliminated without necessarily departing from the spiritand scope of the present invention. It is intended that all mattercontained in the above description or shown in the accompanying drawingsshall be interpreted as illustrative only and not limiting. Changes indetail or structure may be made without departing from the spirit of theinvention.

What is claimed is:
 1. A material handling apparatus comprising: amobile bridge including a first end where material is loaded onto themobile bridge and a second end where material is discharged from themobile bridge, wherein the second end is distal the first end; aconveyance mechanism operatively joined to the mobile bridge andconfigured to move material between the first and second ends of themobile bridge, wherein a first part of the conveyance mechanism at thefirst end where material is loaded is lower than a second part of theconveyance mechanism at the second end where material is discharged; anintermediate transfer mechanism configured to receive material fromexcavation equipment and provide material to the conveyance mechanism;and crawlers that support the mobile bridge and enable the mobile bridgeto be moved.
 2. The material handling apparatus of claim 1 wherein theintermediate transfer mechanism is configured to provide material to theconveyance mechanism in a controlled manner so as not to exceed avolumetric capacity of the conveyance mechanism.
 3. The materialhandling apparatus of claim 1 comprising an adjustment mechanism thatpermits at least one of the crawlers to move relative to a frame of themobile bridge.
 4. The material handling apparatus of claim 1 wherein thecrawlers are orthogonal to a greatest extent of the mobile bridge. 5.The material handling apparatus of claim 1 comprising a shock absorberthat supports the intermediate transfer mechanism.
 6. The materialhandling apparatus of claim 1 comprising a suspension that supports theintermediate transfer mechanism.
 7. The material handling apparatus ofclaim 1 wherein the intermediate transfer mechanism is a transfer bucketor a transfer chute.
 8. The material handling apparatus of claim 1comprising slew bearings that connect the mobile bridge to the crawlers.9. The material handling apparatus of claim 1 wherein the intermediatetransfer mechanism is movable.
 10. The material handling apparatus ofclaim 1 comprising a foot element that is movable between a loweredposition where the foot element rests on the ground and supports theintermediate transfer mechanism, and a raised position where the footelement is spaced apart from the ground.
 11. The material handlingapparatus of claim 1 comprising means for controlling a rate at whichthe intermediate transfer mechanism provides material to the conveyancemechanism.
 12. A material handling apparatus comprising: a mobile bridgeincluding a first end where material is loaded onto the mobile bridgeand a second end where material is discharged from the mobile bridge; aconveyance mechanism operatively joined to the mobile bridge andconfigured to move material between the first and second ends of themobile bridge, wherein a first part of the conveyance mechanism at thefirst end where material is loaded is lower than a second part of theconveyance mechanism at the second end where material is discharged,wherein the second part of the conveyance mechanism is configured todischarge material into haul trucks; an intermediate transfer mechanismconfigured to receive material from excavation equipment and providematerial to the conveyance mechanism; and means for supporting themobile bridge, wherein the means for supporting the mobile bridge ismovable between a raised position where the means for supporting themobile bridge is elevated off the ground and a lowered position wherethe means for supporting the mobile bridge is in contact with theground.
 13. The material handling apparatus of claim 12 wherein theconveyance mechanism comprises an apron feeder.
 14. The materialhandling apparatus of claim 12 wherein the intermediate transfermechanism regulates a rate at which material is transferred from theexcavation equipment to the conveyance mechanism.
 15. The materialhandling apparatus of claim 12 wherein the intermediate transfermechanism regulates a rate at which material is transferred from theexcavation equipment to the conveyance mechanism such that discreteloads from the excavation equipment are gradually discharged onto theconveyance mechanism.
 16. The material handling apparatus of claim 12comprising a skirtboard disposed alongside at least a portion of theconveyance mechanism.
 17. The material handling apparatus of claim 12comprising wheel-mounted frames for carrying a conveyor belt of theconveyance mechanism.
 18. A material handling apparatus comprising: amobile bridge including a first end where material is loaded onto themobile bridge and a second end where material is discharged from themobile bridge; a conveyance mechanism operatively joined to the mobilebridge and configured to move material between the first and second endsof the mobile bridge, wherein the conveyance mechanism is configured tocontinuously provide material to haul tracks at the second end of themobile bridge; and an intermediate transfer mechanism configured toreceive discrete loads of material from excavation equipment and providematerial to the conveyance mechanism, wherein the intermediate transfermechanism controls a rate at which material is provided to theconveyance mechanism.
 19. The material handling apparatus of claim 18wherein the conveyance mechanism comprises an endless conveyor that isconfigurable in a range of angles relative to horizontal.
 20. Thematerial handling apparatus of claim 18 comprising parallel crawlersthat support the mobile bridge and enable the mobile bridge to be moved.21. The material handling apparatus of claim 19 comprising an adjustmentmechanism that permits at least one of the parallel crawlers to moverelative to a frame of the mobile bridge.